function draw_circle(centerx, centery, radius,size)
lix = -radius:1:radius; 
for li = 1:length(lix)
    liy(li) = sqrt(radius^2-lix(li)^2);
end
px = min(max(centerx+lix,1),size);
py1 = min(max(centery+liy,1),size);
py2 = min(max(centery-liy,1),size);
plot(px,py1,'b',px,py2,'b');
            
            